Microsoft's latest tablet PC, the Surface Pro 3, went on sale earlier this month (in the US at least — it doesn't reach the UK until August). With every iteration the Surface Pro improves; this latest version ups the battery life and improves the kickstand to make it easier to type on your lap. And it's great to see Microsoft injecting new energy and thinking back into the PC market again (just don't try to take it apart).

Updating the hardware is good, and Microsoft's continued commitment to the Surface format is likely to make consumers and businesses more comfortable about buying them. The much-rumoured Surface Mini would make a nice addition to the family too.

But for many people, Surface still says more about Microsoft's needs than the needs of its customers: Microsoft needs to make Windows work on tablets, but customers still need convincing that they need to work on Windows tablets.

That's because the way people use tablets is a bit more complicated than just as a straightforward PC replacement. Pitting the Surface Pro 3 against the MacBook Air — and against laptops in general — highlights Microsoft's difficulty in positioning it.

Here's how I think the PC/tablet market is developing.

Consumers: no need for a laptop replacement?

Consumers want multiple screens to use in different ways. For many, tablets are almost (but importantly, not exact) PC replacements. Even a basic tablet will allow consumers to do most things, via a browser or an app. Consumers don't do much word processing or spreadsheet work, but when they do, they've almost certainly still got a PC or laptop somewhere about the place that they can dust down and boot up.

So, for consumers, a tablet that does some but not all of the things a PC can do is perfect — because they've already got a PC. The absence of standard PC features from a tablet is not a limitation, but a selling point (sure, consumers will still buy a laptop at some point, but the refresh cycle will get a lot longer as these devices will be used much less regularly).

The situation is complicated for businesses, too. Many of the tablets in use are brought from home (iPads and Kindle Fires are popular options), but that's accepted because tablets remain additional devices, used for a bit of note taking or the odd presentation.

Professionals: not enough of a laptop replacement?

Windows tablets are undoubtedly attractive to enterprise buyers because these devices will fit in with rest of Windows-powered corporate estate. However, it's unclear how many of those corporate buyers there are these days.

Business users may be happy to use a tablet as an additional screen, but I doubt that the concept Microsoft is pushing, of swapping your laptop for a Surface Pro 3, will appeal to the majority. Read Mary-Jo Foley for a good comparison between the Surface Pro 3 and a Windows 8.1 laptop (spoiler alert: the laptop wins).

If business users don't want to swap their laptop for a Surface, that means Microsoft's hybrid laptop/tablet slips into the category of an additional device. A hybrid tablet that can truly replace a laptop has a decent market to attack. However, a device that will be an expensive additional screen will be a much harder sell.

So where is the use case for something like the Surface Pro 3, and how does it differ from the laptop use case? This is the trickiest part of the problem. Is the ideal user someone who needs a tablet and a laptop, and Windows? Someone who can make notes with a digital pen and do a certain amount of work on a keyboard, but not so much that they need an integrated keyboard? To me, that seems like a relatively limited subset of people (oddly, it matches journalists pretty well).

Market upheaval

Then again, the existence of Surface is itself a reflection of the ongoing upheaval created by the arrival of tablets, which have forced the PC to evolve, mutate and splinter. Nobody has quite figured out how to respond, which is why we'll see plenty more of these hybrid devices over the next few years. But I don't think the idea of trying to combine a tablet with a laptop is entirely the answer.

At the same time, our use of these devices is evolving. One group that Microsoft has been targeting with the Surface range is students, which makes sense. Students don't have the same desktop PC and laptop heritage as older users, so perhaps, freed from the memories of computing past, they will be more willing to embrace a hybrid PC future.

ZDNet's Monday Morning Opener is our opening salvo for the week in tech. As a global site, this editorial publishes on Monday at 8am AEST in Sydney, Australia, which is 6pm Eastern Time on Sunday in the US. It is written by a member of ZDNet's global editorial board, which is comprised of our lead editors across Asia, Australia, Europe, and the US.